Solving the ORA-19279 Error: How to Properly Query XML Data in Oracle SQL

Struggling with `ORA-19279` while parsing XML in Oracle SQL? This guide explains how to fix the XQuery dynamic type mismatch for multiple XML rows.
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Solving the ORA-19279 Error: How to Properly Query XML Data in Oracle SQL

When you encounter the ORA-19279: XPTY0004 - XQuery dynamic type mismatch: expected singleton sequence error while working with XML data in Oracle SQL, it can be frustrating, especially if you're new to querying XML. This error often arises when the structure of your XML and the SQL query do not align properly, leading to unexpected results. In this blog, we’ll break down this common error and provide a clear solution to achieve the desired output from your XML data.

Understanding the Problem

You are trying to parse a SOAP request response that has been converted to XML and utilize it in an SQL query. The given XML structure contains multiple values entries for a key, yet your initial SQL query didn't extract these properly. Instead of getting individual rows for each value, the output flattened them into a single row, which is not what you want. Let’s take a moment to review the XML structure and how it relates to your SQL query.

XML Structure Overview

Here's an excerpt of the XML structure you're dealing with:

[[See Video to Reveal this Text or Code Snippet]]

Initial SQL Query

Your SQL query structure attempted to extract keys and values like so:

[[See Video to Reveal this Text or Code Snippet]]

Encountering the Error

The error appeared when you tried to modify the path for values in the second XMLTABLE, indicating a mismatch in expected types. Instead of getting individual entries for each filename, you were receiving a concatenated string of all values.

The Solution

To resolve this issue, you need to ensure that the SQL query correctly targets the XML structure so that it extracts multiple values as intended. Here’s the revised SQL query that achieves the expected result:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Changes

Updated Path: In the first XMLTABLE:

From: PATH 'value'

To: PATH 'entry/value' to directly access the values.

Key Extraction: Changed the key extraction setting from key to name to match your XML structure.

CROSS JOIN Adjustment: The second XMLTABLE should specifically refer to the path that represents the values, allowing it to return each filename as a distinct row.

Expected Output

After applying these changes, the expected output will correctly present each filename as a separate entry:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By understanding the XML structure and resolving path conflicts in your SQL query, you can effectively eliminate the ORA-19279 error and achieve the desired output. This approach not only helps in fixing the current issue but also sets a solid foundation for future queries involving complex XML structures.

Feel free to reach out in the comments if you have further questions or need additional insights on querying XML in Oracle SQL!